Yes, some of it can, even in its liquid state--if it rises to the top of a volume of water and stays there, and if that's what you mean by "floating in water". Doesn't hotter water tend to do this? All bets are off if you require that at least part of a thing rise above the surface of the volume in order for it to "float in water". I'm not moved much by the "entity in its own right" worry: some molecules , bits , portions or regions of water can float in others; and maybe some kinds of water float in others, just as some gases sink in others. This answer is particularly compelling once someone reminds us of the obvious...

It depends, and even then it depends. It depends first upon whether we ever discover our massive misconceptions. If not, then I imainge we'd continue along merrily piling fancy details upon them. But if (as I think you are imagining) we one day discover that we've gotten it all wrong, then what happens depends upon the inclination of the discoverers, and their culture. There would be shell-shock, certainly, and perhaps some desire to keep heads in the sand and continue on oblivious to the truth. But it's difficult to live by claims we know to be false--try it sometime. And we humans have a genuine built-in urge to understand the way our world works--some say it's what distinguishes us from the other animals. So in all likelihood, we would soon embark upon fresh attempts to understand the way the world actually works--new experiments, new theories, and new conceptual frameworks. I hereby propose, though, that an independent commission be established to determine how on earth we got everything wrong....